The main objective is to develop a radioimmunoassay capable of measuring prolactin in doves and pigeons. In my original research proposal supported by a current research grant, a measurement of prolactin secretion using radioreceptor assay was proposed in investigating the role of prolactin secretion during incubation and on the onset of ovarian recycling in the ring dove. However, the use of the radioreceptor assay for pigeon developed by Dr. J. Buntin of Princeton University has been proved unsatisfactory in measuring the serum prolactin level in doves because of its lack of specificity. In view of this, I am now requesting a supplemental fund to develop a radioimmunoassay (RIA) of plasma prolactin in collaboration with my colleague Dr. H.H. Feder and our new colleague Dr. C.G. Scanes of Cook Campus, who has had experience of successfully developing a RIA of prolactin in the chicken. The immediate objective of developing such an assay is to use it in the studies as originally proposed. Among them are (1) prolactin concentration in females laying fertile vs. infertile eggs and (2) effect of CB-154 and other anti-prolactin agents on plasma prolactin level and crop sac weight.